Simian Crease is also known as single transverse palmar crease. Majority of individuals with simian crease are healthy, however, this condition may also be associated with Down Syndrome. In addition, following conditions may be associated with simian crease: - fetal alcohol syndrome - pseudohypoparathyroidism - Klinefelter syndrome - rubella syndrome - trisomy 13 - cri du chat syndrome Reference: https://www.mountsinai.org/health-library/symptoms/simian-crease Image via: https://www.mountsinai.org/health-library/symptoms/simian-crease